Croaks help frogs locate mates with matching DNA

Washington: Female tree frogs select mates by picking out the one which shares the same DNA as them , by the pitch of croaks they emit, reveals a study.

"To the naked eye -- human and frog, the two frogs look exactly alike," said Carl Gerhardt, professor of biological sciences at the Missouri University College of Arts and Science, who conducted the study with doctoral scholar Mitch Tucker.

The frogs differ only in the number of chromosomes. The eastern grey tree frog has double the number of chromosomes. To the ears of potential mates, these two species differ in their vocal performances, said Gerhardt, according to a university statement.
In previous studies, the scientists found that tree frogs with more sets of chromosome have larger cell sizes, which slows down the trill rate. What was not known was whether the calling preferences of females are similarly linked to chromosome number.

To answer this question, Tucker simulated the chromosome duplication event by replicating spring temperatures early in the frog development. Females were grown to maturity and then exposed to synthetic male calls that differed by trill rate.
They found that the females hopped toward the calls with the trill rate of the males with matching chromosome numbers, which indicates female preference.